package com.csw;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.hadoop.hbase.mapreduce.TableMapReduceUtil;
import org.apache.hadoop.hbase.mapreduce.TableMapper;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

import java.io.IOException;

// 读取HBase的students表中的数据，计算每个班级的学生人数
public class Demo05MapReduceReadHBase {
    public static class ReadHBaseMapper extends TableMapper<Text,IntWritable>{
        @Override
        protected void map(ImmutableBytesWritable key, Result value, Context context) throws IOException, InterruptedException {
            byte[] bytes = key.get();
            String rowkey = Bytes.toString(bytes);
            byte[] bytes1 = value.getValue("info".getBytes(), "clazz".getBytes());
            String clazz = Bytes.toString(bytes1);

            context.write(new Text(clazz),new IntWritable(1));
        }
    }
    public static class MyReducer extends Reducer<Text,IntWritable,Text,IntWritable>{
        @Override
        protected void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
            String clazz = key.toString();

            int sum=0;
            for (IntWritable value : values) {
                sum+=value.get();
            }
            context.write(new Text(clazz),new IntWritable(sum));
        }
    }

    public static void main(String[] args) throws Exception{
        Configuration conf = HBaseConfiguration.create();

        conf.set("hbase.zookeeper.quorum","master:2181,node1:2181,node2:2181");

        //创建Job实例
        Job job = Job.getInstance(conf);
        job.setJarByClass(Demo05MapReduceReadHBase.class);
        job.setJobName("Demo05MapReduceReadHBase");

        Scan scan = new Scan();
        //使用scan做一些过滤
//        scan.setFilter()
        // 配置Mapper
        TableMapReduceUtil.initTableMapperJob(
                TableName.valueOf("students"),
                scan,
                ReadHBaseMapper.class,
                Text.class,
                IntWritable.class,
                job
        );

        //配置Reducer
        job.setReducerClass(MyReducer.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);

        //指定输入输出目录
        FileOutputFormat.setOutputPath(job,new Path("/data/hbase/clazz_num/"));

        job.waitForCompletion(true);
        /**
         *  hadoop jar HBaseAPI-1.0-jar-with-dependencies.jar com.csw.Demo05MapReduceReadHBase
         */
    }
}
